Authorities in Northern Ireland say two nights of rioting in the capital, Belfast, has injured 50 police officers.

The rioting, marked by some of the worst of violence in the British-ruled province in several years, began Saturday, after officials rerouted an annual Protestant parade from a Roman Catholic area.

Witnesses say rioters blocked roads in and around Belfast, threw gasoline bombs at police and set cars on fire. Gunmen also opened fire on police on at least two occasions, but nobody was hit. Police aimed high-pressure streams of water at protesters and fired rubber bullets to break up angry crowds.

The commander of Northern Ireland's police accused the militant Protestant Orange Order of inciting the disturbances, but the group denied responsibility.

The Orange Order sponsors annual marches to remember a historic Protestant victory over Catholic forces in a religious conflict in the 17th century (in 1690). For years Catholics have charged the Protestant parades are aimed at starting trouble. Similar riots in Belfast in July, led by Catholics angered by a Protestant parade, wounded nearly 100 people.